<!doctype html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <title></title> 
    <style type="text/css">
#mes{
	width: 200px;height: 300px;border: 1px solid black;
}

    </style>
</head>
<body>

<script type="text/javascript">
	onload = function(){
		var a = document.createTextNode('askdajdslkajkldjaljk');
		mes.innerHTML='askdajdslkajkldjaljk';
		//mes.
		//mes.replaceChild(a,mes.innerHTML);
		//mes.replaceChild(a);
	}

</script>

<div id='mes'>
	asdl;adk;slal;
</div>
<textarea id='toMes'>
</textarea>
<input type='button' value='发送' id='btn'>
</body>
</html>